System combining power generation apparatus and desalination apparatus

ABSTRACT

In a system combining a power generation apparatus and a desalination apparatus, the power generation apparatus includes a circulation circuit in which a first heat exchanger, an expander, a second heat exchanger having a space, the second heat exchanger for evaporating seawater and generating water vapor, and a working medium pump are connected in series, and a power generator, and the desalination apparatus includes a suction pump for suctioning a gas in the space, a control device for driving the suction pump in such a manner that an atmospheric pressure in the space becomes a saturated water vapor pressure, a condenser for condensing the water vapor led from the space, and a sweet water storage tank for storing sweet water (W) condensed in the condenser.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a system combining a power generation apparatus and a desalination apparatus.

2. Description of the Related Art

Conventionally, a system of generating electric power and also generating sweet water from seawater (performing water generation) is known. For example, Japanese Patent Application Laid-Open No. 2007-309295 discloses a system combining a power generation apparatus and a desalination apparatus. The power generation apparatus includes a circulation circuit in which a first heat exchanger for evaporating a working medium, an expander provided on the downstream side of this first heat exchanger, a second heat exchanger for exchanging heat between the working medium exhausted from this expander and seawater supplied from an exterior, and a working medium pump for feeding the working medium flowing out from this second heat exchanger to the first heat exchanger are connected in series, and a power generator connected to the expander. The desalination apparatus includes a seawater leading flow passage for leading the seawater to the second heat exchanger, a reverse osmosis membrane device having a reverse osmosis membrane for obtaining sweet water from the seawater after going through the second heat exchanger, a pressurization pump for pressurizing the seawater after going through the second heat exchanger and feeding the seawater to the reverse osmosis membrane device, and a sweet water collection tank for collecting the sweet water squeezed out by the reverse osmosis membrane device.

In the power generation apparatus, the expander is driven by the working medium circulated in the circulation circuit, and thereby, the electric power is generated from the power generator. In the desalination apparatus, by feeding the seawater pressurized by the pressurization pump to the reverse osmosis membrane device, the sweet water is squeezed out from the reverse osmosis membrane of the reverse osmosis membrane device.

The reverse osmosis membrane device used in the above system requires regular maintenance of the reverse osmosis membrane in order to prevent a decrease in functions of the reverse osmosis membrane. Further, the pressurization pump used together with the reverse osmosis membrane device is required to pressurize the seawater until a pressure becomes very high in order to squeeze the sweet water out from the reverse osmosis membrane. Therefore, there is a problem that very large electric power is required for driving the pressurization pump.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a system combining a power generation apparatus and a desalination apparatus, the system being capable of generating sweet water without using a reverse osmosis membrane device.

As a means for solving the above problem, the present invention is a system combining a power generation apparatus and a desalination apparatus, the power generation apparatus including a circulation circuit in which a first heat exchanger for evaporating a working medium by exchanging heat between a power generation heat medium supplied from an exterior and the working medium, an expander for expanding the working medium, a second heat exchanger having a predetermined space, the second heat exchanger for condensing the working medium, evaporating seawater, and generating water vapor by exchanging heat between the working medium and the seawater supplied to the space, and a working medium pump for feeding the working medium condensed in the second heat exchanger to the first heat exchanger are connected in series, and a power generator to be driven by expanding the working medium in the expander, and the desalination apparatus including a suction pump for suctioning a gas in the space of the second heat exchanger, a control device for controlling drive of the suction pump, a condenser for condensing the water vapor by exchanging heat between a cooling medium supplied from the exterior and the water vapor led from the space of the second heat exchanger, and a sweet water storage tank for storing sweet water condensed in the condenser.

According to the present invention, since the water vapor is generated by evaporating the seawater in the space of the second heat exchanger and the sweet water is generated by condensing the water vapor by the condenser, a reverse osmosis membrane device like the conventional example can be omitted. Thereby, there are no needs for maintenance of a reverse osmosis membrane and a pressurized pump requiring very large electric power for drive thereof. In particular, in the present invention, the control device controls the drive of the suction pump in such a manner that for example an atmospheric pressure in the space of the second heat exchanger becomes a saturated water vapor pressure. Thus, the seawater in the space is immediately evaporated by receiving heat from the working medium. A sufficient amount of the water vapor generated in such a way is led to the condenser and condensed in the condenser. That is, in the present invention, by lowering the atmospheric pressure in the space by the suction pump, evaporation of the seawater in the space is facilitated. Thus, a sufficient amount of the sweet water is generated. Further, the suction pump only requires such mechanical power that the atmospheric pressure in the space can be lowered to the saturated water vapor pressure. Thus, in comparison to the pressurization pump for squeezing sweet water out from a reverse osmosis membrane as in the conventional example, necessary electric power is reduced.

In this case, preferably, the control device regularly controls to drive the suction pump.

In such a way, by easy control of regularly driving the suction pump, drive electric power of the suction pump can be reduced while suppressing a decrease in water generation efficiency. When the suction pump is always driven, the water generation efficiency becomes the maximum but the drive electric power of the suction pump is increased. Meanwhile, for example when the drive of the suction pump is completely stopped after the atmospheric pressure in the space becomes substantially the saturated water vapor pressure, the drive electric power of the suction pump can be reduced but the external air invades the space of the second heat exchanger or the like and the atmospheric pressure in the space is boosted. Thus, there is a concern that an evaporation amount of the seawater in the space, that is, the water generation efficiency is decreased. On the other hand, by regularly driving the suction pump and making the atmospheric pressure in the space substantially the saturated water vapor pressure, the evaporation of the seawater in the space is facilitated. Thus, the drive electric power of the suction pump can be reduced while suppressing the decrease in the water generation efficiency. Due to simple control of regularly driving the suction pump, the control device can be introduced at low cost.

In the present invention, preferably, the desalination apparatus further has a pressure sensor for detecting an atmospheric pressure in the space of the second heat exchanger, and the control device controls the drive of the suction pump in such a manner that the atmospheric pressure in the space becomes a saturated water vapor pressure when a value detected by the pressure sensor becomes a higher predetermined value than the saturated water vapor pressure of the water vapor in the space.

In such a way, in comparison to a case where the suction pump is regularly driven, the drive electric power of the suction pump can be further suppressed while further suppressing the decrease in the water generation efficiency. That is, when the value detected by the pressure sensor becomes the higher predetermined value than the saturated water vapor pressure of the gas in the space, the suction pump is driven, so as to make the atmospheric pressure in the space the saturated water vapor pressure. Thus, the atmospheric pressure in the space is always maintained between the predetermined value and the saturated water vapor pressure. Therefore, the drive electric power of the suction pump can be reduced while maintaining high water generation efficiency.

In the present invention, preferably, the desalination apparatus further has a temperature sensor for detecting a temperature in the space of the second heat exchanger, and the control device calculates a saturated water vapor pressure at the temperature from the temperature detected by the temperature sensor, and controls the drive of the suction pump with the calculated saturated water vapor pressure as the saturated water vapor pressure of the water vapor in the space.

In such a way, the saturated water vapor pressure can be more precisely determined in accordance with the temperature in the space. Thus, performance of reducing the drive electric power of the suction pump can be more enhanced while maintaining high water generation efficiency.

In the present invention, preferably, the desalination apparatus further includes an evaporator for evaporating the seawater by exchanging heat between a desalination heat medium supplied from the exterior and the seawater, an evaporator pump for feeding the seawater into the evaporator, a first leading flow passage for leading water vapor to the first heat exchanger in such a manner that the water vapor generated in the evaporator is utilized as the power generation heat medium for the first heat exchanger, and a second leading flow passage for leading the sweet water condensed in the first heat exchanger to the sweet water storage tank.

In such a way, the water vapor generated by the evaporation of the seawater in the evaporator is used as the power generation heat medium for the first heat exchanger and by exchanging heat between the water vapor and the working medium, the water vapor is condensed to become the sweet water and led to the sweet water storage tank. Thus, a water generation amount can be efficiently increased. In other words, in this invention, a water generation system which is different from the water generation system for obtaining the sweet water by condensing the water vapor generated in the space of the second heat exchanger is added, and this added water generation system has a function of heating the working medium and a function of performing the water generation at the same time.

In the present invention, preferably, the seawater is used as the cooling medium for the condenser.

In such a way, since there is no need for particularly preparing an exclusive medium as the cooling medium, manufacturing cost for desalination is reduced.

In the present invention, preferably, the desalination apparatus further includes a solar collector for heating the desalination heat medium supplied to the evaporator.

In such a way, in comparison to a case where fossil fuel is combusted to heat the desalination heat medium, generation of carbon dioxide and the like can be prevented.

As described above, according to the present invention, the system combining the power generation apparatus and the desalination apparatus, the system being capable of generating the sweet water without using the reverse osmosis membrane device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a system combining a power generation apparatus and a desalination apparatus according to an embodiment of the present invention; and

FIG. 2 is a diagram showing major parts of a modified example of the system shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A system combining a power generation apparatus 100 and a desalination apparatus 200 of an embodiment of the present invention will be described with reference to FIG. 1.

The power generation apparatus 100 is provided with a circulation circuit 10 through which a working medium is circulated, and a power generator 15. It should be noted that a working medium whose boiling point is lower than water (such as R245fa) is used as the working medium.

The circulation circuit 10 is a closed circuit in which a first heat exchanger 11 for evaporating the working medium, an expander 12 for expanding the working medium, a second heat exchanger 13 for condensing the working medium exhausted from the expander 12, and a working medium pump 14 for feeding the working medium condensed in the second heat exchanger 13 to the first heat exchanger 11 are connected in series via pipes.

The first heat exchanger 11 is to evaporate and bring the liquid working medium into wet vapor, saturated vapor, or superheated vapor. The first heat exchanger 11 has a working medium flow passage 11 a through which the working medium flows, and a heat medium flow passage 11 b through which a power generation heat medium supplied from a heat source of an exterior flows. The working medium flow passage 11 a is connected to the pipe of the circulation circuit 10. That is, one end of the working medium flow passage 11 a is connected to the pipe provided between the working medium pump 14 and the first heat exchanger 11, and the other end of the working medium flow passage 11 is connected to the pipe provided between the first heat exchanger 11 a and the expander 12. The working medium flowing through the working medium flow passage 11 a is evaporated by exchanging heat with the power generation heat medium flowing through the heat medium flow passage 11 b. In the present embodiment, water vapor M generated by a solar collector 40 with solar as a heat source to be described later is used as the power generation heat medium flowing through the heat medium flow passage 11 b. However, this power generation heat medium is not limited to this.

The expander 12 is provided on the downstream side of the first heat exchanger 11 in the circulation circuit 10, and takes motion energy out from the working medium by expanding the working medium evaporated in the first heat exchanger 11. In the present embodiment, a screw expander is used as the expander 12. In the screw expander, a pair of male and female screw rotors (not shown) is accommodated in a rotor chamber (not shown) formed in a casing of the expander. In this screw expander, the screw rotors are rotated by an expansion force of the working medium supplied to the rotor chamber from an intake opening which is formed in the casing. The working medium whose pressure is lowered by expansion in the rotor chamber is exhausted from an exhaust opening formed in the casing. In the present embodiment, a temperature of the working medium exhausted from this exhaust opening is about 60° C. It should be noted that the expander 12 is not limited to the screw expander but may be a scroll expander or the like.

The second heat exchanger 13 has a main body portion in which a predetermined space 13 a is formed, and a working medium flow passage 13 b inside which the working medium flows, the working medium flow passage being provided so as to pass through in an interior of this space 13 a. The working medium flow passage 13 b is connected to the pipes of the circulation circuit 10. That is, one end of the working medium flow passage 13 b is connected to the pipe provided between the expander 12 and the second heat exchanger 13, and the other end of the working medium flow passage 13 b is connected to the pipe provided between the second heat exchanger 13 and the working medium pump 14. Since surface-layer seawater S is supplied into this space 13 a from the exterior, the working medium flow passage 13 b is soaked into the seawater S. The second heat exchanger 13 condenses the working medium by exchanging heat between the seawater S supplied to the space 13 a and the working medium flowing in the working medium flow passage 13 b. At this time, although the seawater S is evaporated and the water vapor M is generated in the space 13 a, this water vapor M will be described later. The gas working medium exhausted from the expander 12, for example the working medium of about 60° C. and 200 kPa flows into this working medium flow passage 13 b of the second heat exchanger 13. The liquid working medium condensed by exchanging heat with the seawater S, for example the working medium of about 33° C. and 200 kPa flows out from this working medium flow passage 13 b.

The working medium pump 14 is provided on the downstream side of the second heat exchanger 13 in the circulation circuit 10 (between the second heat exchanger 13 and the first heat exchanger 11), to circulate the working medium in the circulation circuit 10. This working medium pump 14 pressurizes the liquid working medium condensed in the second heat exchanger 13 to a predetermined pressure and feeds the working medium to the first heat exchanger 11. A centrifugal pump provided with an impeller as a rotor, a gear pump whose rotor includes a pair of gears, or the like is used as the working medium pump 14.

The power generator 15 is connected to the expander 12, and driven by expanding the working medium in the expander 12 and driving the screw rotors. Specifically, the power generator 15 has a rotation shaft connected to one of the pair of screw rotors of the expander 12, and electric power is generated by rotating this rotation shaft in accordance with rotation of the screw rotors. In the present embodiment, a power generation amount of about 100 kW is obtained from this power generator 15.

Next, the desalination apparatus 200 will be described. This desalination apparatus 200 has a first water generation system 201, a second water generation system 202, and a sweet water storage tank 203 for storing sweet water W. The first water generation system 201 is a system for performing water generation by utilizing the water vapor M generated in the space 13 a of the second heat exchanger 13. The second water generation system 202 is a system for performing the water generation by utilizing the water vapor M generated in a space 33 a of an evaporator 33 to be described later.

The first water generation system 201 is provided with a gas flow passage 20 inside which a gas flows, a suction pump 21 for suctioning the gas, a condenser 22 for condensing the water vapor M by exchanging heat between the seawater S serving as a cooling medium supplied from the exterior and the water vapor M, a water vapor leading flow passage 23 for leading the water vapor M in the space 13 a of the second heat exchanger 13 to the condenser 22, a cooling medium flow passage 24 inside which the cooling medium flows, a condenser pump 25 provided in this cooing medium flow passage 24, a sweet water leading flow passage 27 for leading the sweet water condensed in the condenser 22 to the sweet water storage tank 203, a sweet water feed-out pump 28 provided in this sweet water leading flow passage 27, a seawater supplement flow passage 29 for supplementing the seawater S to the space 13 a of the second heat exchanger 13, a second heat exchanger pump 30 provided in this seawater supplement flow passage 29, for feeding the seawater S into the space 13 a, a control device 31, a temperature sensor 32 a for detecting a temperature in the space 13 a of the second heat exchanger 13, and a pressure sensor 32 b for detecting an atmospheric pressure in the space 13 a of the second heat exchanger 13. The second water generation system 202 is provided with the evaporator 33 for condensing a desalination heat medium and evaporating the seawater S by exchanging heat between the desalination heat medium supplied from the exterior and the seawater S, a seawater supplement flow passage 34 for supplementing the seawater S to the evaporator 33, an evaporator pump 35 provided in this seawater supplement flow passage 34, a first leading flow passage 36 for leading the water vapor M generated in the evaporator 33 to the first heat exchanger 11, a second leading flow passage 37 for leading the sweet water condensed in the first heat exchanger 11 to the sweet water storage tank 203, a circulation circuit 38 for circulating the desalination heat medium, a circulation pump 39 provided in this circulation circuit 38, and the solar collector 40 for heating the desalination heat medium.

Firstly, the first water generation system 201 will be described.

The condenser 22 has a main body portion in which a predetermined space 22 a is formed. One end of the gas flow passage 20 is connected to the space 22 a, and the suction pump 21 is provided in this gas flow passage 20. The water vapor leading flow passage 23 connects the space 13 a of the second heat exchanger 13 and the space 22 a of the condenser 22. Therefore, when the suction pump 21 is driven, the gas in the space 13 a of the second heat exchanger 13 is discharged to the other end side of the gas flow passage 20 through the water vapor leading flow passage 23 and the space 22 a of the condenser 22.

The cooling medium flow passage 24 is provided so as to pass through in an interior of the space 22 a, and both ends thereof are arranged in the seawater S. Therefore, the condenser pump 25 feeds the seawater S into the cooling medium flow passage 24. In the present embodiment, a temperature of this seawater S is for example 25° C. It should be noted that the cooling medium used in this condenser 22, that is, the cooing medium flowing in the cooling medium flow passage 24 is not limited to the seawater S.

The sweet water leading flow passage 27 connects the condenser 22 and the sweet water storage tank 203, and the sweet water feed-out pump 28 feeds the sweet water W in the condenser 22 to the sweet water storage tank 203.

The sweet water supplement flow passage 29 is a flow passage for supplementing the seawater S to the space 13 a of the second heat exchanger 13. In the present embodiment, the temperature of this seawater S is for example 25° C. However, the seawater S supplemented to the space 13 a may be low-temperature seawater, that is, deep-layer seawater S. This is because more electric power can be obtained from the power generator 15. That is, this is because the electric power obtained from the power generator 15 is more increased as a pressure of the working medium on the exhaust side of the expander 12 is lower, and the pressure of the working medium on the exhaust side of the expander 12 is more lowered as the temperature of the seawater S supplied to the space 13 a is lower.

The control device 31 has a recording unit 31 a in which a saturated water vapor pressure in accordance with the temperature is recorded, a calculation unit 31 b for calculating the saturated water vapor pressure at the temperature from a value detected by the temperature sensor 32 a by referring to the recording unit 31 a, a pump driving unit 31 c for driving the suction pump 21 when a value detected by the pressure sensor 32 b becomes a predetermined value determined by only adding a fixed value to the saturated water vapor pressure in the space 13 a calculated by the calculation unit 31 b, and a pump stopping unit 31 d for stopping drive of the suction pump 21 when the value detected by the pressure sensor 32 b becomes the saturated water vapor pressure or less.

Before starting the water generation in this first water generation system 201, the seawater S is charged in the space 13 a, and there is sometimes a case where the atmospheric pressure in the space 13 a in this state is higher than the predetermined value. In this case, when the water generation in the first water generation system 201 is started, the pump driving unit 31 c drives the suction pump 21, and the gas in the space 13 a is suctioned by the suction pump 21 and discharged to the other end side of the gas flow passage 20. When the atmospheric pressure in the space 13 a becomes the saturated water vapor pressure or less, the pump stopping unit 31 d stops the drive of the suction pump 21.

In this state, that is, a state that the atmospheric pressure in the space 13 a and the space 22 a becomes the saturated water vapor pressure, the seawater S in the space 13 a is immediately evaporated by receiving heat from the working medium circulated in the circulation circuit 10. It should be noted that in the present embodiment, a temperature of the water vapor M generated at this time is for example 31° C., and the saturated water vapor pressure thereof is 4.50 kPa. When the water vapor M is generated in the space 13 a in such a way, the atmospheric pressure in the space 13 a becomes higher than the atmospheric pressure in the space 22 a of the condenser 22. Thus, the water vapor M is led to the space 22 a of the condenser 22 through the water vapor leading flow passage 23, and condensed by exchanging heat with the seawater S in the cooling medium flow passage 24. The sweet water W generated in such a way is led to the sweet water storage tank 203 through the sweet water leading flow passage 27. Since the water vapor M reaching from the interior of the space 13 a of the second heat exchanger 13 to the space 22 a of the condenser 22 is condensed in the condenser 22, a state that the atmospheric pressure in the space 13 a is higher than the atmospheric pressure in the space 22 a is maintained. Therefore, the water vapor M generated in the space 13 a is naturally led to the space 22 a.

Next, the second water generation system 202 will be described.

The evaporator 33 has a main body portion in which the predetermined space 33 a is formed. The circulation circuit 38 is provided so as to pass through in an interior of this space 33 a, and the desalination heat medium flows inside thereof. This circulation circuit 38 has a heat medium flow passage 33 b arranged in the space 33 a. By providing the seawater S into this space 33 a from the exterior, the heat medium flow passage 33 b is soaked into the seawater S.

The seawater supplement flow passage 34 is a flow passage for supplementing the seawater S to the space 33 a of the evaporator 33. The seawater S is fed to the space 33 a by the evaporator pump 35. The seawater S supplemented through this seawater supplement flow passage 34 is required to be evaporated by exchanging heat with the desalination heat medium. Thus, the temperature thereof is preferably higher, that is, the seawater is preferably surface-layer seawater S.

The first leading flow passage 36 connects the space 33 a of the evaporator 33 and the one end side of the heat medium flow passage lib of the first heat exchanger 11, and the second leading flow passage 37 connects the other end side of the heat medium flow passage 11 b of the first heat exchanger 11 and the sweet water storage tank 203.

When the water generation in this second water generation system 202 is started, the evaporator pump 35 and the circulation pump 39 are driven. Thereby, the desalination working medium is pressurized by the circulation pump 39 and circulated in the circulation circuit 38. That is, the desalination working medium is fed to the side of the solar collector 40 by the circulation pump 39, evaporated by being heated by this solar collector 40, and then flows into the heat medium flow passage 33 b of the evaporator 33. This desalination working medium is condensed by exchanging heat with the seawater S in the space 33 a of the evaporator 33, and circulated in the circulated circuit 38 by flowing out from the evaporator 33 and reaching the circulation pump 39 again.

At this time, in the evaporator 33, the seawater S is evaporated by receiving heat from the desalination heat medium, so that the water vapor M is generated. This water vapor M is led to the heat medium flow passage 11 b of the first heat exchanger 11 through the first leading flow passage 36, and condensed by exchanging heat with the working medium circulated in the working medium flow passage 11 a, so as to become the sweet water. This sweet water W is led to the sweet water storage tank 203 through the second leading flow passage 37.

That is, this second water generation system 202 utilizes the water vapor M generated in a process of generating the sweet water W from the seawater S as the power generation heat medium for the power generation apparatus 100. Thus, the second water generation system also has a function of heating the working medium in addition to a function of performing the water generation.

As described above, according to the system combining the power generation apparatus 100 and the desalination apparatus 200 of the present embodiment, since the water vapor M is generated by evaporating the seawater S in the space 13 a of the second heat exchanger 13 and the sweet water W is generated by condensing the water vapor M in the condenser 22, a reverse osmosis membrane device as in the conventional example can be omitted. Thereby, there are no needs for maintenance of a reverse osmosis membrane and a pressurized pump requiring very large electric power for drive thereof. In particular, in this embodiment, the control device 31 drives the suction pump 21 in such a manner that the atmospheric pressure in the space 13 a of the second heat exchanger 13 becomes the saturated water vapor pressure. Thus, the seawater S in the space 13 a is immediately evaporated by receiving heat from the working medium. A sufficient amount of the water vapor M generated in such a way is led to the condenser 22 and condensed in the condenser 22. That is, in the present embodiment, by making the atmospheric pressure in the space 13 a the saturated water vapor pressure by the suction pump 21, evaporation of the seawater S in the space 13 a is facilitated. Thus, a sufficient amount of the sweet water W is generated. Further, the suction pump 21 only requires such mechanical power that the atmospheric pressure in the space 13 a can be lowered to the saturated water vapor pressure. Thus, in comparison to the pressurization pump for squeezing sweet water out from the reverse osmosis membrane as in the conventional example, necessary electric power is reduced.

The control device 31 of the present embodiment drives the suction pump 21 in such a manner that the atmospheric pressure in the space 13 a becomes the saturated water vapor pressure when the value detected by the pressure sensor 32 b becomes a higher predetermined value than the saturated water vapor pressure of the water vapor M in the space 13 a. Thus, drive electric power of the suction pump 21 can be suppressed while suppressing a decrease in water generation efficiency. That is, when the suction pump 21 is always driven, the water generation efficiency becomes the maximum but the drive electric power of the suction pump 21 is increased. Meanwhile, when the drive of the suction pump 21 is completely stopped after the atmospheric pressure in the space 13 a of the second heat exchanger 13 becomes the saturated water vapor pressure, the external air invades the space 13 a or the like and the atmospheric pressure in the space 13 a is boosted. Thus, there is a concern that an evaporation amount of the seawater in the space 13 a, that is, the water generation efficiency is decreased. On the other hand, by driving the suction pump 21 and making the atmospheric pressure in the space 13 a the saturated water vapor pressure when the value detected by the pressure sensor 32 b becomes the higher predetermined value than the saturated water vapor pressure of the gas in the space 13 a, the atmospheric pressure in the space 13 a is always maintained between the predetermined value and the saturated water vapor pressure. Therefore, the drive electric power of the suction pump 21 can be reduced while maintaining high water generation efficiency.

In the present embodiment, the water vapor M generated by evaporating the seawater S in the evaporator 33 is used as the power generation heat medium for the first heat exchanger 11 and by exchanging heat with the working medium, the water vapor M is condensed to become the sweet water W and led to the sweet water storage tank 203. Thus, a water generation amount can be efficiently increased. In other words, the desalination apparatus 200 of the present embodiment has the second water generation system 202 which is different from the first water generation system 201 for obtaining the sweet water W by condensing the water vapor M generated in the space 13 a of the second heat exchanger 13, and this second water generation system 202 has the function of heating the working medium and the function of performing the water generation at the same time.

It should be noted that the embodiment disclosed herein is thought to be not restriction but an example in all aspects. The scope of the present invention is indicated not by the above description of an embodiment but by the claims, and further includes equivalent meanings to the claims and all modifications within the scope.

For example, the above embodiment shows the example that the water vapor M generated by the solar collector 40 is used as the power generation heat medium for the first heat exchanger 11. However, the power generation heat medium is not limited to this. This power generation heat medium may be vapor or hot water taken from a well (steam well), vapor or hot water exhausted from a plant and the like, or vapor, hot water, or the like generated from a boiler having biomass or fossil fuel as a heat source. However, from a point of the water generation amount, the water vapor M generated by evaporating the seawater S in the evaporator 33 is preferably used.

The above embodiment shows the example that the control device 31 drives the suction pump 21 based on the values detected by the temperature sensor 32 a and the pressure sensor 32 b. However, the temperature sensor 32 a and the pressure sensor 32 b may be omitted, the pump driving unit 31 c of this control device 31 may drive the suction pump 21 after a fixed time elapses from stoppage of the suction pump 21, and the pump stopping unit 31 d may stop the suction pump 21 after a predetermined time elapses from the drive of the suction pump 21. It should be noted that in this case, the recording unit 31 a and the calculation unit 31 b are also omitted. Even in this case, the drive electric power of the suction pump 21 can be suppressed while suppressing the decrease in the water generation efficiency. That is, by regularly driving the suction pump 21 and making the atmospheric pressure in the space 13 a the saturated water vapor pressure, the evaporation of the seawater S in the space 13 a is facilitated. Thus, the drive electric power of the suction pump 21 can be reduced while suppressing the decrease in the water generation efficiency. In this case, due to simple control of regularly driving the suction pump 21, the control device 31 can be constructed at low cost.

The above embodiment shows the example that the desalination heat medium is heated by the solar collector 40. However, this desalination heat medium may be heated by vapor or hot water taken from a well (steam well), vapor or hot water exhausted from a plant and the like, or vapor, hot water, or the like generated from a boiler having biomass or fossil fuel as a heat source.

As shown in FIG. 2, a deaeration tube 41, a seawater flow passage 42, and a deaeration tube pump 43 may be added to the first water generation system 201. The deaeration tube 41 is provided between the condenser 22 and the suction pump 21 in the gas flow passage 20. This deaeration tube 41 has a main body portion in which a predetermined space 41 a is formed, and a connection flow passage 41 b for connecting the space 41 a and the space 22 a of the condenser 22. The seawater flow passage 42 is provided so as to pass through in an interior of the space 41 a, and the seawater S flows inside thereof. The deaeration tube pump 43 is provided in the seawater flow passage 42, and feeds the seawater S into the seawater flow passage 42. It should be noted that in the present embodiment, the temperature of this seawater is for example 25° C.

In such a way, in a case where the first water generation system 201 includes the deaeration tube 41, the seawater flow passage 42, and the deaeration tube pump 43 and when the suction pump 21 is driven, the water vapor M in the space 22 a reaches to the space 41 a of the deaeration tube 41, and is condensed in the space 41 a by exchanging heat with the seawater S flowing in the seawater flow passage 42. The sweet water W generated in such a way is returned to the interior of the space 22 a through the connection flow passage 41 b. In such a way, even when the water vapor M in the space 22 a of the condenser 22 is suctioned to the side of the suction pump 21 at the time of driving the suction pump 21, the water vapor M is condensed in the deaeration tube 41 and returned to the condenser 22. Thus, generation of failure that the water vapor M in the space 22 a of the condenser 22 is suctioned by the suction pump 21 and the water generation amount is lowered is suppressed. 

What is claimed is:
 1. A system combining a power generation apparatus and a desalination apparatus, said power generation apparatus comprising: a circulation circuit in which a first heat exchanger for evaporating a working medium by exchanging heat between a power generation heat medium supplied from an exterior and the working medium, an expander for expanding the working medium, a second heat exchanger having a predetermined space, the second heat exchanger for condensing the working medium, evaporating seawater, and generating water vapor by exchanging heat between the working medium and the seawater supplied to the space, and a working medium pump for feeding the working medium condensed in said second heat exchanger to said first heat exchanger are connected in series; and a power generator to be driven by expanding the working medium in said expander, and said desalination apparatus comprising: a suction pump for suctioning a gas in the space of said second heat exchanger; a control device for controlling drive of said suction pump; a condenser for condensing the water vapor by exchanging heat between a cooling medium supplied from the exterior and the water vapor led from the space of said second heat exchanger; and a sweet water storage tank for storing sweet water condensed in said condenser.
 2. The system combining the power generation apparatus and the desalination apparatus according to claim 1, wherein said control device regularly controls to drive said suction pump.
 3. The system combining the power generation apparatus and the desalination apparatus according to claim 1, wherein: said desalination apparatus further has a pressure sensor for detecting an atmospheric pressure in the space of said second heat exchanger; and said control device controls the drive of said suction pump in such a manner that the atmospheric pressure in the space becomes a saturated water vapor pressure when a value detected by said pressure sensor becomes a higher predetermined value than the saturated water vapor pressure of the water vapor in the space.
 4. The system combining the power generation apparatus and the desalination apparatus according to claim 3, wherein: said desalination apparatus further has a temperature sensor for detecting a temperature in the space of said second heat exchanger; and said control device calculates a saturated water vapor pressure at the temperature from the temperature detected by said temperature sensor, and controls the drive of said suction pump with the calculated saturated water vapor pressure as the saturated water vapor pressure of the water vapor in the space.
 5. The system combining the power generation apparatus and the desalination apparatus according to claim 1, wherein said desalination apparatus further comprises: an evaporator for evaporating the seawater by exchanging heat between a desalination heat medium supplied from the exterior and the seawater; an evaporator pump for feeding the seawater into said evaporator; a first leading flow passage for leading water vapor to said first heat exchanger in such a manner that the water vapor generated in said evaporator is utilized as the power generation heat medium for said first heat exchanger; and a second leading flow passage for leading the sweet water condensed in said first heat exchanger to said sweet water storage tank.
 6. The system combining the power generation apparatus and the desalination apparatus according to claim 1, wherein the seawater is used as the cooling medium for said condenser.
 7. The system combining the power generation apparatus and the desalination apparatus according to claim 5, wherein said desalination apparatus further comprises a solar collector for heating the desalination heat medium supplied to said evaporator. 